How to test HTTP Keep alive is actually working

I know HTTP keep-alive is on by default in HTTP 1.1 but I want to find a way to开发者_开发知识库 confirm that it is actually working.

Does anyone know of a simple way to test from a web browser (EG how to make sense of wireshark). I know I need to look for multiple HTTP requests over the same TCP connection but I don't know how to confirm that in wireshark or any other way.

Thanks!

As Ron Garrity said on ServerFault, you can use Curl like this:

curl -Iv http://www.aptivate.org 2>&1 | grep -i 'connection #0'

And it outputs these two lines if keep-alive is working:

* Connection #0 to host www.aptivate.org left intact
* Closing connection #0

And if keep-alive is not working, then it just outputs this line:

* Closing connection #0

If you're on Windows Vista or later, you can use Resource Manager. The Network tab will list all open TCP connections and the process they were started by. Open a browser with one tab, browse to your page, and test.

First, try to capture the traffic to the target website in Wireshark and limit it to what you need with a filter like:

tcp port 80 and host targetwebsite.com

Then load the page in a browser or fetch it by any tool you have. If the target web page refreshes itself or one of the values in it, leave it open until you have at least one change in it.

Now you have enough data and you can stop capturing procedure in Wireshark.

You should see dozens of records and their protocol should be TCP or HTTP. For the purpose of your quick simple check, you will not need TCP records. So, lets remove them by applying another filter. In top of the window there is a "filter" field. Type http there, and wireshark will hide all records but those which have a HTTP protocol.

Now select a record and look at the next level of details, which you can find in the 2nd box bellow all records. Just to be sure you are looking at the right place, the first line there starts with "Frame XYZ". The fourth line starts with "Transmission Control Protocol". Look for the port numbers after "SRC Port" and "DST Port:". Depending on the record, one of these numbers belongs to the webserver (typically 80) and the other one shows port number in your end.

Now check a couple of different GET records. To know if the request is a GET record, check the Info column. If the port numbers in your end are used several times, all those requests were made through HTTP keepalive.

Remember that most browsers will open multiple connections, even if the webserver supports keepalive. So, DO NOT conclude your evaluation by finding just one different port.

1. The most accurate way is to curl the same URL multiple times.

curl -v http://weibo.com -o /dev/null http://weibo.com -o /dev/null

If the output contains Re-using existing connection, then the HTTP keep-alive feature is working. For example,

* TCP_NODELAY set
* Connected to weibo.com (180.149.138.251) port 80 (#0)
> GET / HTTP/1.1
> Host: weibo.com
> User-Agent: curl/7.68.0
> Accept: */*
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 301 Moved Permanently
< ...
< ...
< 
{ [236 bytes data]
* Connection #0 to host weibo.com left intact
* Found bundle for host weibo.com: 0x56324121d9a0 [serially]
* Can not multiplex, even if we wanted to!
* Re-using existing connection! (#0) with host weibo.com
* Connected to weibo.com (180.149.138.251) port 80 (#0)
> GET / HTTP/1.1
> Host: weibo.com
> User-Agent: curl/7.68.0
> Accept: */*
> 
* Mark bundle as not supporting multiuse
< HTTP/1.1 301 Moved Permanently
< ...
< ...
< 
{ [236 bytes data]
* Connection #0 to host weibo.com left intact

2. Another quick way is to test with ab. But some HTTP servers might not return the Connection: keep-alive header even when they've already turned on keep-alive feature, such as uwsgi. In such cases, ab does NOT send keep-alive requests. That makes ab can only do "positive" detection on HTTP keep-alive.

ab -c 5 -n 50 -k https://www.google.com/

If the result shows

...
Complete requests:      50
Failed requests:        0
Keep-Alive requests:    50    # Pay attention to this line
Total transferred:
...

Then the HTTP keep-alive is enabled.